Withdrawal due to unknown or unspecified psychoactive substance

**Definition:** Withdrawal due to unknown or unspecified psychoactive substance is a clinically significant cluster of symptoms, behaviours and/or physiological features, varying in degree of severity and duration, that occurs upon cessation or reduction of use of an unknown or unspecified substance in individuals who have developed dependence or have used the unknown or unspecified substance for a prolonged period or in large amounts. Withdrawal due to unknown or unspecified psychoactive substance can also occur when prescribed psychoactive medications have been used in standard therapeutic doses. The specific features of the withdrawal state depend on the pharmacological properties of the unknown or unspecified substance.